Field of the Disclosure
The following relates generally to wireless communication, and more specifically to a timestamp repair mechanism in case of decompression failure.
Description of Related Art
Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems. A wireless multiple-access communications system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).
A wireless communication system (e.g., 3rd Generation Partnership Project (3GPP), Long Term Evolution (LTE), etc.) may use robust header compression (RoHC) to provide header information in an efficient manner. For example, when voice data is transmitted in a conventional Internet Protocol (IP) format, voice packets may be carried via Real-time Transport Protocol (RTP) or User Datagram Protocol (UDP). RTP/UDP/IP messages have a relatively large header overhead (e.g., greater than the voice data payload). Bandwidth utilization may be improved by using RoHC to compress the RTP/UDP/IP header.
RoHC divides the header into a static section including information that does not change between adjacent packets during transmission (e.g., IP address, port number, etc.) and a dynamic section including information that changes for each packet (e.g., sequence number (SN), timestamp (TS), IP identifier (IP-ID), etc.). A compressor at an upstream device (e.g., a base station) and a decompressor at a downstream device (e.g., UE), for example, both store a context for each data stream. Absent a decompression failure, the compressor includes the static section of the header only in the initial message of the data stream, while the dynamic section is included in further compressed messages. Thus, the decompressor decompresses the initial message to obtain the static information and the dynamic information, and decompresses subsequent messages to obtain only dynamic information.
RoHC may use a Window-based Least Significant Bits (WLSB) algorithm to compress the SN, TS and IP-ID, which change relatively little between packets of a data stream. In general, the WLSB algorithm provides the lowest k bits of an original field value for transmission instead of the whole original field value, with the compressor and decompressor storing a reference value for the field in the context for the data stream. The decompressor restores the original field value using the reference value and the received k bits. The decompressor searches in an interpretation interval for a decoded value with the same lowest k bits as the received k bits.
When a loss of successive compressed headers transmitted by the upstream device occurs (e.g., due to radio interface) such that a new compressed header that carries unscaled TS bits is received by the downstream device, for example, decompression of the header may fail. As described herein, there is a need for improving header recovery to reduce re-initialization and re-synchronization, which otherwise may lead to loss of packets and a poor compression rate.